It is known in the art to realize gas burners, in particular domestic burners for cooking foods, that are substantially shaped in three or four separated parts which may be mutually assembled. In particular, it is known to realize gas burners composed of a cup, provided with coupling means to a hob, an intermediate body, or burner head, provided with one or more delivering chambers of the fuel mixture and at least one flame-spreader, integral with or separated from such an intermediate body, and with one or more closing lids. The cup is usually provided, as well, with means for feeding a fuel gas, or directly a fuel mixture, to the delivering chamber/chambers of the intermediate body and, in a lot of cases, it may be provided with a mixer, or part thereof, to mix the fuel gas with primary air coming from the outer environment.
Mainly in case wherein the burner is required to delivery a high thermal power, it is known to make at least one mixer with axial Venturi effect, having an horizontal axis or an axis tilted with respect to the horizontal line, connected to the burner cup, which has, as well, a support for at least one corresponding injector of the fuel gas arranged so that to direct the gas flow into such a mixer with axial Venturi effect.
The carrying out of a mixer with axial Venturi effect inside the burner cup, which is substantially a hollow tubular element provided with at least one region with a section gradually increasing from a region with a narrow section, usually needs the fastening of a number of metal parts, for example by welding, and/or complex chip removal machining, starting from one or more semi-finished items obtained by casting or die-casting.
In fact, the coupling of a hollow tubular body, as the mixer with axial Venturi effect, with a concave body, such as the cup, entails the presence of undercuts, and then it is not simple to be realized, above all if a cup in a single piece, or with the assembling of few components, is to be made. In this latter case, it is thus common to obtain a cup, by a casting or die-casting method in an apposite mould, in which the mixer with axial Venturi effect is made, completely or in part, separately from the cup and then it is inserted in the latter, and fastened thereto, only after these components have been die formed.
Such a method for manufacturing a gas burner with a cup provided with a mixer with axial Venturi effect, proves to be difficult to be implemented, complex to realize and very expensive.
It is then an object of the present invention to realize a method for the manufacturing of a burner provided with a cup having at least one tubular hollow part of a mixer with axial Venturi effect which does not present the drawbacks of the known previous art and then which allows to manufacture such a burner simply and not excessively expensive.
It is another object of the present invention to provide a method for the manufacturing of a burner provided with a cup having at least one part of the tubular region with an increasing section of a mixer with axial Venturi effect which leads to the manufacturing of a cup in a single piece, that thus has very resistant structure, and at the same time it is suitable for a gas burner designed to deliver a high thermal power.
It is another object of the present invention to realize a gas burner of the above mentioned type in which the cup, provided with at least part of the tubular region with an increasing section of a mixer with axial Venturi effect, is obtained as a whole by casting or die-casting, so that, in addition to be quick and easy to manufacture, it is also highly resistant from a mechanical point of view.